kiji-rest: REST-90. Allow KijiREST to be started in foreground mode, via the 'foreground' command line option.

Signed-off-by: Jonathan Natkins <natty@wibidata.com>
commit: https://github.com/kijiproject/kiji-rest/commit/e7e232cb4c48707477e70f0ae7c14e4dc09da9ec